Resistance toBean common mosaic necrosis virusConferred by thebc-1Gene Affects Systemic Spread of the Virus in Common Bean

alleles, isolate NL8-CA was able to systemically infect only a small proportion of upper uninoculated leaves (less than 13 and 3%, respectively). The whole genomes of isolates 1755b, TN1a, and NL8-CA were sequenced and sequence analysis revealed that, despite the overall high nucleotide sequence identity between PG-III and PG-VI isolates (approximately 96%), two areas of the BCMNV genome in the P1/HC-Pro and HC-Pro/P3 cistrons appeared to be more divergent between these two pathotypes of BCMNV. The data suggest that the phenotypic differences among PG-III and PG-VI isolates of BCMNV in common bean cultivars from host resistance groups 2, 3, and 9 carrying bc-1 alleles were related to the impaired systemic movement of the PG-III isolates to the upper, uninoculated leaves, and also suggest a role of the recessive bc-1 gene in interfering with systemic spread of BCMNV.